NASA Astronauts Use Marathon Spacewalk to Make Repairs on ISS

As those who have seen The Martian witnessed, an astronaut has to be a jack of all trades, handy with everything from their scientific specialty to making repairs on everything inside (and outside) their space ship. Two NASA astronauts on the International Space Station (ISS) used this dogged determination during a marathon, almost eight-hour spacewalk on Friday to make “high-flying plumbing” repairs, according to the space agency.

Americans Scott Kelly, who is the current station commander, and flight engineer Kjell Lindgren took their second spacewalk in the last nine days. Friday’s spacewalk had them venturing outside the ISS’s U.S. Quest airlock into the vacuum of space for seven hours and 48 minutes (longer than planned). During that time, the duo made the final repairs to resolve an issue that ISS residents have been dealing with since 2012.

The Photovoltaic Thermal Control System was designed to cool by dissipating heat generated at the ISS from radiators attached to its truss structure. The cooling system had operated through a backup loop for the past few years, since a spacewalk in November 2012 by astronauts Sunita Williams and Aki Hoshide re-routed the ISS plumbing to a backup radiator to try and isolate the source of a potentially hazardous ammonia leak. However, the leak persisted and was eventually traced to a different part, which was replaced during a May 2013 spacewalk by NASA astronauts Chris Cassidy and Tom Marshburn.

After demonstrating that the cooling system is now leak free, the latest spacewalk sought to restore the original cooling system configuration. The astronauts restored the truss ammonia cooling system on the port side to its original configuration, disconnecting a spare cooling system on the craft that had been in place for three years to circumvent the persistent ammonia leak. It also involved returning the ammonia levels to the desired intensity in both the prime and back-up systems using storage tanks.

During the spacewalk, which was the 190th outside the ISS and sixth this year, the astronauts had to synchronize their actions to accomplish the complicated tasks involved in reconfiguring and adding the ammonia to the port-side station cooling systems.Russian cosmonaut Sergey Volkov and Japanese astronaut Kimiya Yui, who are also current ISS residents, assisted the pair of spacewalkers into their spacesuits and the airlock before the depressurization began and out of their suits upon completion.

There was one minor glitch on the long spacewalk to reconfigure the cooling system. The astronauts ran out of time to stow the backup Thermal Control Radiator they had retracted. NASA had hoped to pack away the spare, but Kelly and Lindgren ran out of time to fold and cover its extended radiator panels.

The ISS, which orbits approximately 250 miles overhead, has been continually occupied for 15 years now. The size of a football field, the ISS circles the globe every 90 minutes. Five space agencies involving 15 countries built and operate the craft, which took more than 40 U.S. and Soviet flights to build module by module and the nearly 200 spacewalks to maintain. The marathon spacewalk to make repairs that NASA astronauts made Friday is expected to be the last ISS spacewalk this year.